#pragma once
#include <algorithm>
#include <cstdint>
#include <cstring>

// Based on https://github.com/vog/sha1
/*
Original authors:
Steve Reid (Original C Code)
Bruce Guenter (Small changes to fit into bglibs)
Volker Grabsch (Translation to simpler C++ Code)
Eugene Hopkinson (Safety improvements)
Vincent Falco (beast adaptation)
*/
namespace cinatra{
namespace sha1 {

	static std::size_t constexpr BLOCK_INTS = 16;
	static std::size_t constexpr BLOCK_BYTES = 64;
	static std::size_t constexpr DIGEST_BYTES = 20;

	inline std::uint32_t rol(std::uint32_t value, std::size_t bits) {
		return (value << bits) | (value >> (32 - bits));
	}

	inline std::uint32_t blk(std::uint32_t block[BLOCK_INTS], std::size_t i) {
		return rol(
			block[(i + 13) & 15] ^ block[(i + 8) & 15] ^
			block[(i + 2) & 15] ^ block[i], 1);
	}

	inline void R0(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
		z += ((w&(x^y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
		w = rol(w, 30);
	}


	inline void R1(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
		block[i] = blk(block, i);
		z += ((w&(x^y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
		w = rol(w, 30);
	}

	inline void R2(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
		block[i] = blk(block, i);
		z += (w^x^y) + block[i] + 0x6ed9eba1 + rol(v, 5);
		w = rol(w, 30);
	}

	inline void R3(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
		block[i] = blk(block, i);
		z += (((w | x)&y) | (w&x)) + block[i] + 0x8f1bbcdc + rol(v, 5);
		w = rol(w, 30);
	}

	inline void R4(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
		block[i] = blk(block, i);
		z += (w^x^y) + block[i] + 0xca62c1d6 + rol(v, 5);
		w = rol(w, 30);
	}

	inline void make_block(std::uint8_t const* p, std::uint32_t block[BLOCK_INTS]) {
		for (std::size_t i = 0; i < BLOCK_INTS; i++)
			block[i] =
			(static_cast<std::uint32_t>(p[4 * i + 3])) |
			(static_cast<std::uint32_t>(p[4 * i + 2])) << 8 |
			(static_cast<std::uint32_t>(p[4 * i + 1])) << 16 |
			(static_cast<std::uint32_t>(p[4 * i + 0])) << 24;
	}

	template<class = void>
	void transform(std::uint32_t digest[], std::uint32_t block[BLOCK_INTS]) {
		std::uint32_t a = digest[0];
		std::uint32_t b = digest[1];
		std::uint32_t c = digest[2];
		std::uint32_t d = digest[3];
		std::uint32_t e = digest[4];

		R0(block, a, b, c, d, e, 0);
		R0(block, e, a, b, c, d, 1);
		R0(block, d, e, a, b, c, 2);
		R0(block, c, d, e, a, b, 3);
		R0(block, b, c, d, e, a, 4);
		R0(block, a, b, c, d, e, 5);
		R0(block, e, a, b, c, d, 6);
		R0(block, d, e, a, b, c, 7);
		R0(block, c, d, e, a, b, 8);
		R0(block, b, c, d, e, a, 9);
		R0(block, a, b, c, d, e, 10);
		R0(block, e, a, b, c, d, 11);
		R0(block, d, e, a, b, c, 12);
		R0(block, c, d, e, a, b, 13);
		R0(block, b, c, d, e, a, 14);
		R0(block, a, b, c, d, e, 15);
		R1(block, e, a, b, c, d, 0);
		R1(block, d, e, a, b, c, 1);
		R1(block, c, d, e, a, b, 2);
		R1(block, b, c, d, e, a, 3);
		R2(block, a, b, c, d, e, 4);
		R2(block, e, a, b, c, d, 5);
		R2(block, d, e, a, b, c, 6);
		R2(block, c, d, e, a, b, 7);
		R2(block, b, c, d, e, a, 8);
		R2(block, a, b, c, d, e, 9);
		R2(block, e, a, b, c, d, 10);
		R2(block, d, e, a, b, c, 11);
		R2(block, c, d, e, a, b, 12);
		R2(block, b, c, d, e, a, 13);
		R2(block, a, b, c, d, e, 14);
		R2(block, e, a, b, c, d, 15);
		R2(block, d, e, a, b, c, 0);
		R2(block, c, d, e, a, b, 1);
		R2(block, b, c, d, e, a, 2);
		R2(block, a, b, c, d, e, 3);
		R2(block, e, a, b, c, d, 4);
		R2(block, d, e, a, b, c, 5);
		R2(block, c, d, e, a, b, 6);
		R2(block, b, c, d, e, a, 7);
		R3(block, a, b, c, d, e, 8);
		R3(block, e, a, b, c, d, 9);
		R3(block, d, e, a, b, c, 10);
		R3(block, c, d, e, a, b, 11);
		R3(block, b, c, d, e, a, 12);
		R3(block, a, b, c, d, e, 13);
		R3(block, e, a, b, c, d, 14);
		R3(block, d, e, a, b, c, 15);
		R3(block, c, d, e, a, b, 0);
		R3(block, b, c, d, e, a, 1);
		R3(block, a, b, c, d, e, 2);
		R3(block, e, a, b, c, d, 3);
		R3(block, d, e, a, b, c, 4);
		R3(block, c, d, e, a, b, 5);
		R3(block, b, c, d, e, a, 6);
		R3(block, a, b, c, d, e, 7);
		R3(block, e, a, b, c, d, 8);
		R3(block, d, e, a, b, c, 9);
		R3(block, c, d, e, a, b, 10);
		R3(block, b, c, d, e, a, 11);
		R4(block, a, b, c, d, e, 12);
		R4(block, e, a, b, c, d, 13);
		R4(block, d, e, a, b, c, 14);
		R4(block, c, d, e, a, b, 15);
		R4(block, b, c, d, e, a, 0);
		R4(block, a, b, c, d, e, 1);
		R4(block, e, a, b, c, d, 2);
		R4(block, d, e, a, b, c, 3);
		R4(block, c, d, e, a, b, 4);
		R4(block, b, c, d, e, a, 5);
		R4(block, a, b, c, d, e, 6);
		R4(block, e, a, b, c, d, 7);
		R4(block, d, e, a, b, c, 8);
		R4(block, c, d, e, a, b, 9);
		R4(block, b, c, d, e, a, 10);
		R4(block, a, b, c, d, e, 11);
		R4(block, e, a, b, c, d, 12);
		R4(block, d, e, a, b, c, 13);
		R4(block, c, d, e, a, b, 14);
		R4(block, b, c, d, e, a, 15);

		digest[0] += a;
		digest[1] += b;
		digest[2] += c;
		digest[3] += d;
		digest[4] += e;
	}

} // sha1

struct sha1_context {
	static unsigned int constexpr block_size = sha1::BLOCK_BYTES;
	static unsigned int constexpr digest_size = 20;

	std::size_t buflen;
	std::size_t blocks;
	std::uint32_t digest[5];
	std::uint8_t buf[block_size];
};

template<class = void>
inline void init(sha1_context& ctx) noexcept {
	ctx.buflen = 0;
	ctx.blocks = 0;
	ctx.digest[0] = 0x67452301;
	ctx.digest[1] = 0xefcdab89;
	ctx.digest[2] = 0x98badcfe;
	ctx.digest[3] = 0x10325476;
	ctx.digest[4] = 0xc3d2e1f0;
}

template<class = void>
inline void update(sha1_context& ctx,
	void const* message, std::size_t size) noexcept {
	auto p = reinterpret_cast<
		std::uint8_t const*>(message);
	for (;;) {
		auto const n = (std::min)(
			size, sizeof(ctx.buf) - ctx.buflen);
		std::memcpy(ctx.buf + ctx.buflen, p, n);
		ctx.buflen += n;
		if (ctx.buflen != 64)
			return;
		p += n;
		size -= n;
		ctx.buflen = 0;
		std::uint32_t block[sha1::BLOCK_INTS];
		sha1::make_block(ctx.buf, block);
		sha1::transform(ctx.digest, block);
		++ctx.blocks;
	}
}

template<class = void>
inline void finish(sha1_context& ctx, void* digest) noexcept {
	using sha1::BLOCK_INTS;
	using sha1::BLOCK_BYTES;

	std::uint64_t total_bits =
		(ctx.blocks * 64 + ctx.buflen) * 8;
	// pad
	ctx.buf[ctx.buflen++] = 0x80;
	auto const buflen = ctx.buflen;
	while (ctx.buflen < 64)
		ctx.buf[ctx.buflen++] = 0x00;
	std::uint32_t block[BLOCK_INTS];
	sha1::make_block(ctx.buf, block);
	if (buflen > BLOCK_BYTES - 8) {
		sha1::transform(ctx.digest, block);
		for (size_t i = 0; i < BLOCK_INTS - 2; i++)
			block[i] = 0;
	}

	/* Append total_bits, split this uint64_t into two uint32_t */
	block[BLOCK_INTS - 1] = total_bits & 0xffffffff;
	block[BLOCK_INTS - 2] = (total_bits >> 32);
	sha1::transform(ctx.digest, block);
	for (std::size_t i = 0; i < sha1::DIGEST_BYTES / 4; i++) {
		std::uint8_t* d =
			reinterpret_cast<std::uint8_t*>(digest) + 4 * i;
		d[3] = ctx.digest[i] & 0xff;
		d[2] = (ctx.digest[i] >> 8) & 0xff;
		d[1] = (ctx.digest[i] >> 16) & 0xff;
		d[0] = (ctx.digest[i] >> 24) & 0xff;
	}
}
}
